When I was looking through the new edition of The Filmmaker's Handbook, I noticed a lot of little changes and additions. An example: In a list of equipment to bring to the set, in the lighting category I noticed one addition: "dimmer boxes." I can't argue with that -- dimmer boxes help one light with finesse, and they're fairly easy to come by. I went to the trouble of making a couple dimmers (aka "hand squeezers") myself about a year and a half ago. I made a couple of 600 watt boxes, as well as a 1000 watt box. The supplies I got from the local home improvement store, though I remember that the 1000w dimmer was not widely available. If I remember correctly, I built all three dimmer for about $100 in supplies. They would have been cheaper, but the 1000w dimmer was considerably more expensive than the 600w.
In retrospect, instead of making those boxes, I would have been better off simply purchasing one of the many dimmer boxes or router speed controls (which can be used as a dimmer box) that are commercially available. They're cheaper, they're probably more reliable than anything I could build, and the heavy duty router speed controls can handle more power than the ones I built. Plus, the router speed controls have a safety fuse, which my self-built dimmers lack.
Shopping for some last week, I ran across lots of varieties. Here are some:
Dimmer Boxes:
Ikea Dimma - 300 Watts and under - $7.95 Note: Not useful for most motion picture lights, but if you just need something for practicals, these are nice and cheap.
Smith Victor - DC-1 Dimmer Control
Router Speed Controls:
Harbor Freight Tools - 15 Amps and lower - $19.99
MLCS Router Speed Control - 15 Amps and lower - $20.95 and $28.95, respectively, for the "home" and "industrial/commercial" use boxes
Grizzly G3555 Router Speed Control
Rockler Router Speed Control - 20 Amps and lower - $39.99
If, however, you wish to build your own, you can find instructions in Blain Brown's Motion Picture and Video Lighting, 2nd Edition